模拟信号压缩与解压matlab.doc

function y,g_out = expanderint16clip(x,fd,g_in,m)%expander% y = expanderint16clip(x,fd,g_in,m)%x - the input signal array%fd - the full deviated amplitude%g_in - the initial gain%m - update the expander gain every m samples%y - the expanded signal array%g_out - the output gain%companding specificationn% compression ratio 2:1% crossover point 60% of full audio deviation% attack time 3.3 ms% recovery time 14.85 ms%int16_scale = 32768;persistent ae ae_1 average counter mean old_x_array ae1 ae1_1 ae2 ae2_1 ae_diff ae_diff_1;%initializationif isempty(ae) ae1 = float2fract(0.99436); ae1_1 = 231 - fract2longfract(ae1); %float2longfract(1-0.99436); ae2 = float2fract(0.99985); ae2_1 = 231 - fract2longfract(ae2); %float2longfract(1-0.99985); ae_diff = float2fract(0.9995); ae_diff_1 = 231 - fract2longfract(ae_diff); counter = 0; average = 0; mean = 0; old_x_array = zeros(1,40);endue = fractmult(float2fract(0.6366),fd);ae = ae1;ae_1 = ae1_1;global mean_e_g average_e_g diff_e_g avg_dif_e_g ge_g flag_e_g avg_dif_float_e_g; %test onlyavg_dif = 0;avg_dif_float = 0; %test onlyoneforty = float2fract(1/40);temp1 = 0;temp2 = 0;scale_flag = 0;for i = 1:length(x) abstract = abs(x(i); temp1 = longlongfractmult(temp1,ae) + longlongfractmult(ae_1,abstract); %averager. divide 215 for fractional multiplication. average = longfract2fract(temp1); average_e_g(i) = average; %test only mean = mean - fractmult(oneforty,old_x_array(1) + fractmult(oneforty,abstract); %update mean mean_e_g(i)= mean; %test only if counter = 0 %update gain every m times g_in = average/ue; g_in_floor = floor(g_in); g_in_fract = float2fract(g_in - floor(g_in); counter = m; end ge_g(i) = g_in; %test only old_x_array(1:39) = old_x_array(2:40); old_x_array(40) = abs(x(i); difference = abs(mean-average); diff_e_g(i) = difference; %test only average_e_g(i) = average; %test only if difference fractmult(mean,float2fract(0.1) %0.1*mean avg_dif = fract2longfract(difference); %scale up 6 bits to prevent fix-point effect in calculating average difference avg_dif_float = difference; %test only ae = ae1; ae_1 = ae1_1; flag_e_g(i) = 0; %test only else avg_dif = longlongfractmult(ae_diff_1,difference) + longlongfractmult(avg_dif,ae_diff); avg_dif_float = difference + 0.9995*(avg_dif_float-difference); %test only if avg_dif = int16_scale - 1 temp = int16_scale - 1; end if temp fractmult(mean,float2fract(0.1) %0.1*mean avg_dif = fract2longfract(difference); %scale up 6 bits to prevent fix-point effect in calculating average difference avg_dif_float = difference; %test only ac = ac1; ac_1 = ac1_1; flag_g(i) = 0; %test only else avg_dif = longlongfractmult(ac_diff_1,difference) + longlongfractmult(avg_dif,ac_diff); avg_dif_float = difference + 0.9995*(avg_dif_float-difference); %test only if avg_dif